What is the difference between an MSDS and an SDS?

There is no difference regarding the document. It is just a different name.

MSDS means Material Safety Data Sheet. This is the old name. SDS means Safety Data Sheet and is the new name which is used from now on.

Sometimes you will receive an e-SDS, which means extended Safety Data Sheet. This is a common SDS with in the attachment the Exposure Scenarios as they are REACH registered together with the substance concerned.